This is a continuing project designed to determine the specific substances and cellular control mechanisms that underlie the tumorous state in the crown gall disease of plants. Essentially three different but related areas of the problem are being investigated. These may be listed as follows: (1) Studies will continue in an attempt to characterize the precise chemical structure of a cell-division-promoting factor that is synthesized persistently by plant tumor cells and that plays a central role in the development of a capacity for autonomous growth of those cells. (2) The chemical nature and mode of action of a cAMP (3'5')-like compound found in normal plant cells and plant tumor cells will be studied further. This compound, although showing certain characteristics of cAMP(3'5'), differs from authentic cAMP(3'5') in a number of essential respects and appears to play a role in the regulation of the cell division process in higher plant species. (3) Studies on the persistent but potentially reversible suppression of the tumorous state as well as of a recovery from that state will continue during the next year. The persistent suppression of the tumorous state has been found to be regulated by positive feedback control mechanisms while a recovery from that state occurs during meiosis rather than during later stages of the sexual reproductive process.